Effects of chemical short-range order on displacement cascade in medium-entropy CrCoNi alloys

Abstract

Chemical short-range order (CSRO) is an important structure in high/medium entropy alloys (H/MEAs), which has a significant influence on the mechanical properties of irradiated materials. In this work, molecular dynamics (MD) simulations are performed to investigate the effects of CSRO on the point defect evolution during displacement cascade in medium-entropy CrCoNi alloys. To validate the influence of CSRO on point defects, multi-displacement cascades were initially conducted on the alloy. The results indicate that the CSRO structure can notably diminish dislocation and defect densities. Then, the influence of the CSRO structure on point defects under single displacement cascade was discussed. Both the peak number of point defects and the number of surviving point defects decrease with the increasing degree of CSRO during the single displacement cascade, indicating that the CSRO enhances the irradiation-resistance of irradiated materials. The Ni-rich region in CSRO can inhibit the formation of point defects due to its higher formation energy barrier. While the Co-Cr region in CSRO was found to promote the migration of point defects that can facilitate their recombination due to the lower migration energy. The current work provides new insights into understanding the evolution of irradiation-induced defects and mechanical properties of irradiated M/HEAs.